Many parents are concerned that sitting too close to a television screen may affect their children's vision. Various devices have been proposed to address the problem.
One prior art approach involves installing a controller in the television receiver itself. The controller uses a proximity sensor to detect whether an object is proximate to the receiver's screen, and generates an audible or visual warning signal through the speakers or screen of the television receiver itself. Such systems are described in U.S. Pat. No. 4,835,614 to Ryu, U.S. Pat. No. 4,831,448 to Park, and U.S. Pat. No. 5,355,180 to Back. A significant shortcoming is that the controller is built into the television receiver and does not lend itself to retrofitting an existing receiver.
U.S. Pat. No. 5,541,664 to Cuadrado describes a viewing distance controller that is entirely external to a television receiver. The television receiver is plugged into a power socket associated with the controller. The controller has a distance sensor that detects the proximity of an object to the screen, and a timing circuit that switches power to the socket and thus the television receiver in response to distance violations. The controller can be readily used with various television receivers but shutting off power to a contemporary television receiver has the undesirable effect of clearing all settings preprogrammed by a user.
U.S. Pat. No. 4,417,270 to Hensliegh et al describes another system for controlling viewing distance. An acoustic proximity'sensor is used to detect whether a child is too close to a television receiver. An interference generator then radiates high energy pulses into the circuitry of the television receiver to disrupt the screen image.